Paging

• Paging is a memory management mechanism used to access processes from the secondary storage into the main memory in the form of pages.
• Paging divides each process in the form of pages.
• The main memory is divided into small fixed-size blocks of physical memory, which are called frames.
• The basic idea behind the paging is to remove the external fragmentation and gain faster access to the data.
• The size of a frame should be kept the same as that of a page to have maximum utilization of the main memory and to avoid external fragmentation.

Effect of Page Size on Performance of the OS

• In paging, the number of frames is always equal to the size of memory divided by the page size.
• So, an increase in page size means a decrease in the number of available frames.
• Having fewer frames will increase the number of page faults, because it provides less freedom in page replacement strategies.
• Large page sizes also waste space due to Internal Fragmentation.
• Large page size also draws in more memory per fault. Hence, the number of faults may decrease if there is limited contention.
• Larger pages also reduce the number of TLB misses.
• Small Page size increases the number of pages as well as the size of a page table.
• Hence large page size is preferred most of the time.
• But it is not fixed, sometimes a small page size is preferred or sometimes a larger page size is preferred.
• It is dependent on the nature of the problem or system requirements.